152 SEASONAL CHANGES AND HISTORIES. 



allied species in Europe, and in half a dozen or 

 more of these we find quite similar disparities, all 

 of which are in the same direction. 



The European Tortoise-shell (Aglais urticae), 

 for example, is generally double-brooded ; occa- 

 sionally a triple brood is mentioned ; it is one 

 of the commonest of European butterflies, and 

 reaches from the North Cape to the Mediterra- 

 nean ; our congeneric species, the Nettle Tortoise- 

 shell [see Fig. 127], is rarely found south of the 

 northernmost parts of the United States, and yet 

 it is triple-brooded in all parts of Canada. Everes 

 Amyntas, again, occurs throughout Europe, with 

 the exception of certain northern and northwest- 

 ern portions, and is double -brooded ; our Tailed 

 Blue [see Fig. 125], named for the resemblance to 

 its European congener, and by some careless 

 authors considered identical with it, is also a wide- 

 spread insect ; but even in New England, which 

 is toward the northern limit of its range, it is 

 triple-brooded. The wide-spread European blues, 

 Rusticus Argus and R. Aegon, the Silver-studded 

 Blue, are usually placed among monogoneutic in- 

 sects, and the latter certainly has only a single 

 brood in England (where it is the only one of the 

 two found) ; Meyer Diir is in fact almost the only 

 author who claims these species as digoneutic ; 

 both of them occur in southern Europe ; the 

 American Pearl-studded Yiolet (Rusticus Scud- 



